"We've looked hard at the problems caused by very popular exhibitions... and decided to take action," gallery director Nicholas Penny told The Times.
Advance booking opens on Tuesday.
In a statement, the gallery said it expected there to be "unprecedented demand" for tickets and advised patrons to book in advance.
Its decision to reduce the number of admissions, it added, had been "in response to visitors' comments regarding overcrowding in exhibitions".
Longer opening hours and the decision to open the exhibition on 1 January 2012 will add 20% to normal capacity, it said.
"The message from the National Gallery is to book early... and to come prepared," its statement reads.
According to the gallery, Leonardo Da Vinci: Painter at the Court of Milan will bring together "the largest ever number of Leonardo's rare surviving paintings".
The "landmark" exhibition, which includes works never shown in the UK before, runs from 9 November 2011 to 5 February 2012.
Concentrating on da Vinci's career as a court painter in Milan in the 1480s and 1490s, it will display more than 60 paintings and drawings by the artist.
These include his acknowledged masterpiece The Lady with an Ermine, the Belle Ferronniere and the National Gallery's own recently restored Virgin of the Rocks.
A full-scale copy of his famous Last Supper, on loan from the Royal Academy, will also be included.
But speculation that the exhibition might feature the Mona Lisa proved to be unfounded.
The gallery's decision to limit numbers follows outbreaks of what one art critic termed "gallery rage" as visitors struggled to view works of art on display due to large crowds at various so-called "blockbuster" exhibitions.
Messages on the Tate's online message board earlier this year suggested some visitors were left frustrated by crowding at the gallery's Gauguin exhibition.
Although some contributors felt the numbers of people were to be expected for such a popular artist, one Gauguin fan wrote: "Would have preferred the exhibition if it had been less busy.
"Almost impossible to see the pictures, and reflecting upon them was impossible in such a crowd. Had travelled from Edinburgh to see exhibition, will think twice about going to a London show again."
Visit View Best in The word for Daily Updated Animal Funny Pictures Collection